In a conventional X-ray image system, X-rays emitted from an X-ray source can pass through an object to be imaged, and primary beams of the X-rays can be incident upon a digital image detector so as to form a projected image in a digital radiography imaging. However, scattered beams are generated when the primary beams are passing through the object, and these scattered beams may reduce the image contrast and degrade the image quality. In order to remove these undesired scattered beams, anti-scatter grid array is typically used between the X-ray source and the image detector. A conventional anti-scatter grid array is composed of alternating stripes made of an X-ray transmission material such as aluminum or carbon and an X-ray absorbing material such as lead. The anti-scatter grid array preferentially transmits the primary beams of the X-rays and absorbs the scattered beams. However, due to the grid pattern of the X-ray absorbing material, the anti-scatter grid array will cast a shadow onto the image detector, and thus will form visible artifacts in the X-ray image, commonly referred to as grid line artifacts. In order to reduce the grid line artifacts, a band-stop filter can often be used. Such filtering in the frequency domain is in fact a process of convoluting the X-ray image in the spatial domain. However, while using the band-stop filter for filtering to reduce the grid line artifacts, ringing artifacts will be induced by the band-stop filter in the process of convolution due to the asymmetric intensity distribution on the X-ray image.
Therefore, it is necessary to further reduce the generation of the ringing artifacts in the X-ray image in the process of the grid line artifacts reduction, so as to improve the image quality.